Sliding-Mode Perturbation Observer-Based Delay-Independent Active Mitigation for AGC Systems Against False Data Injection and Random Time-Delay Attacks

This article presents a sliding-mode perturbation observer (SMPO) based delay-independent active mitigation (DIAM) scheme for automatic generation control (AGC) systems of multi-area interconnected power grid. It is designed to defend against malicious cyber attacks such as false data injection attack (FDIA), random time-delay attack (RTDA), and coordinated cyber attack (CCA) in the measurement channel and control channel. In the DIAM scheme, perturbation terms are introduced to describe the comprehensive effects of injected false signals and random delay components caused by cyber attacks. SMPO is designed for each control area of AGC systems to reconstruct the perturbations in the measurement channel and control channel based on the equivalent output injection method. The cyber attacks are mitigated by compensating the perturbation terms based on the accurate perturbation estimations provided by SMPO. The proposed DIAM is a delay-independent scheme which does not require any time-delay knowledge, and it is able to deal with the coordinated attacks of FDIA and RTDA at the same time. Simulation studies and experimental tests are undertaken on a three-area AGC systems to demonstrate the performance of the proposed DIAM scheme.